The answer will vary depending on what's in your soil mix.
I have found that allowing the pots to dry out and feel light when you lift them is the first step. When they're dry enough to water, I take these steps:
First I will mist, spray, or shower water onto the top of the soil, which should look and feel completely dry at this time. Doing so helps the water absorb into the soil evenly, instead of just having soil float on top of the water, or having the water leak down between the soil and the side of the pot.
Next I have my water, which is normal tap water that I let sit for 24-48 hours before using to disperse chlorine and dissolved gases. I add nutrients if it's time to feed, then I will PH adjust my water based on my current soil PH.
Then I slowly and evenly water the pot, either turning the pot as I pour, or moving my water/nutes around as I pour. I do this in 1/2 gallon increments. 2 Liter increments would work for those using the metric system. In between pourings I wait about 30-60 seconds, then pour another 1/2 gallon. I continue doing this until I start seeing runoff (water dripping out of the pot and into the collection pan).
As your plant grows, the amount of water needed may vary, so using one set number of gallons may not always be effective. You'll need to watch closely each time you water.
The key is letting that soil really dry out between waterings. The top of the soil should be completely dry, and the soil inside should start drying out as well, which will force the roots to grow down and out in search of more water. Bigger roots will support a bigger plant, and especially bigger and better buds.